The overall goal of this project is to develop a safe and effective vaccine against the strains of group A streptococci that may trigger acute rheumatic fever. Previous studies have shown that M proteins, the major protective antigens of these organisms, contain both protective as well as potentially harmful tissue-crossreactive epitopes. Therefore, the experiments outlined in this proposal will provide detailed information regarding the primary structures of M proteins containing protective antigenic determinants which can then be separated from autoimmune epitopes. The specific aims are: 1) to determine the protective and tissue-crossreactive immunogenicity of purified "rheumatogenic" M proteins in laboratory animals, 2) to determine the primary structures of the amino-termini of M proteins, 3) to synthesize peptides copying limited regions of the M proteins and test their protective and tissue-crossreactive immunogenicity, and 4) to construct multivalent subunit vaccines containing only protective epitopes that will be based on either synthetic peptides or recombinant DNA structures. M proteins will be purified from E. coli expressing M protein genes that are cloned using specific DNA fragments generated by the polymerase chain reaction. The purified molecules will be tested for protective and tissue-crossreactive immunogenicity in rabbits and mice. Primary structures of the amino-termini of M proteins will be determined by nucleotide sequencing of the emm genes or in some cases by Edman degradation of the purified M proteins. Overlapping peptides will be synthesized and tested for the presence of protective epitopes will be combined and covalently linked to carriers to formulate multivalent vaccines. Synthetic oligonucleotides encoding protective epitopes will be ligated into expression vectors to produce multivalent M protein vaccines. These studies should provide detailed information on the structure and immunological function of M proteins that will be directly related to the development of vaccines to prevent the streptococcal infections that may trigger rheumatic fever.